New Zealand introduces a “star rating” system for foods – despite absence of any evidence that it will work

Public health campaigners are fortunate that the labelling changes they demand from industry are not subject to the same requirement for supporting evidence that the food industry is asked to produce for its marketing messages.

Because if they were, the addition of traffic light labels or other front-of-pack “healthy rating” systems would never go ahead.

And yet, despite the scarcity of evidence that such systems cause people to make healthier choices – as well as criticism from researchers of the simplistic and out-of-date science that underpins such systems – another country has decided to embrace them.

It’s New Zealand making the decision this time, adopting a star system (see picture). The country’s Minister of Food Safety was quoted as saying that the system, “will have a positive effect on consumers’ ability to identify healthier food products.”

She did not say that it would change their food choices – wisely, given the absence of any evidence that such systems have any beneficial effect.

In fact, as one published academic study has pointed out, “revealed preference data analyses do not support that these tendencies translate into healthy behaviours at point of sale.”

Or as another study, published in the journal Appetite in July 2013 pointed out (The Effects of Nutrition Label Format and Product Assortment on the Healthfulness of Food Choice, authors Aschemann-Witzel et al), despite the presence of such rating systems, they did not cause consumers to make healthier choices unless they were prompted to by the researchers.

Even one of the most vocal advocates of front of pack systems – and specifically traffic lights – Dr. Mike Rayner of the Oxford University Heart Foundation Health Promotion Group, has authored a report that found no effect on sales. Published in 2010 in the World Health Organisation’s journal Health Promotion Interntional, the study tracked ready meal and sandwich sales at an un-named retailer for a month before and after the introduction of traffic light labelling.

It found no significant difference in sales. In fact the healthiest two sandwiches experienced the sharpest drop in sales of any product: “This study found the introduction of traffic light labels had no discernible effect on the relative healthiness of consumer purchases.”

In a separate real-world study, one company we know of found that sales of its products that had a “negative” red label actually increased! Some people were buying food for pleasure, not only for health, and had decided that the red ones had more of the fat and other things that give good taste.

It is unlikely that there will be any improvement in public health in New Zealand as a result of its new labelling system. Nevertheless, some health professionals will continue to let their views be guided by “belief” rather than evidence.

Young health professionals coming up through the ranks should take note of this and try not to fall victim to the intellectual laziness that seems to have taken over some of their elders.

Reversing the tide of obesity and related diseases is not going to be accomplished by fiddling with labels. Obesity is a product of food culture (in English-speaking countries snacking between meals, for example, is much more common than in some other cultures) and the amount of time we spend doing exercise. Or rather not doing exercise, but sitting in cars and in front of computers and TV screens. Only when we tackle what is a highly complex and nuanced problem in a nuanced way, with a long-term plan to enable people to move more, will we make improvements in public health.